1. Field of the Invention
The invention relates to electronic devices including integrated circuit sensors, imagers and other sensing devices. More particularly, the invention relates to improved scratch and mechanical resistance for integrated circuit devices including integrated circuit sensors, other sensing devices and other electronic devices.
2. Description of the Related Art
Sensing devices including integrated circuit (IC) devices such as those used for capacitive sensors desire scratch resistant surfaces to protect the integrated circuit from repeated contact by external elements. For example, in capacitive sensors such as fingerprint sensors, the ridges and valleys on the finger tip making contact with the surface of the sensor (e.g., a CMOS chip) form variations in capacitance across a dielectric material in the chip that can be measured by an array of sensing elements arranged within the chip. The capacitance variations are then output by the sensor and used to form an image of the fingerprint.
Conventional sensors of this kind typically provide one or more layers including mechanically firm dielectric materials, e.g., silicon nitride (Si.sub.3 N.sub.4), silicon dioxide (SiO.sub.2), and aluminum oxide (Al.sub.2 O.sub.3). Also, the sensing elements and interconnect wires, which typically are formed on top of, within or below the dielectric region, typically are made of aluminum, copper, chromium, alloys of these metals, or multi-layers of these metals, because of their relatively low resistivities. For example, see the capacitive sensors disclosed in U.S. Pat. No. 4,353,056, issued to Tsikos, and U.S. Pat. No. 5,325,442, issued to Knapp.
However, sensors including integrated circuit sensors having such arrangements are still susceptible to scratches from the stress of repeated touch and from sharp, pointed external elements (e.g., fingernails and writing instruments). Such scratches and mechanical stress effects degrade the performance and/or functionality of the device and often lead to the complete failure of the device. Therefore, it is desirable to provide a sensor in general and an integrated circuit sensing device in particular having an improved scratch resistance and mechanical resistance over existing devices.